The present invention relates to a tape reel and a magnetic tape which are applied to a magnetic tape cassette, and more particularly to the tape reel provided with an upper and a lower flanges at an upper and a lower end of a reel hub, and the magnetic tape to be wound around the tape reel.
Conventionally, there have been various types of magnetic tape cassettes, namely, for a video recorder, audio apparatus, computer, etc. For example, there has been a type of the magnetic tape cassette for the video recorder which includes a cassette case consisting of an upper and a lower cassette half and a pair of tape reels having a reel hub and an upper and a lower flange rotatably contained in the cassette case in a state where a magnetic tape is wound around the reel hub.
FIG. 5 shows a basic structure of the above described tape reel. As shown in the drawing, a tape reel 110 includes a reel hub 111 around which a magnetic tape 120 is wound, an upper flange 112 fixed to an upper end of the reel hub 111, and a disc-like lower flange 113 integrally formed at a lower end of the reel hub 111. In this example, a lower face of the upper flange 112 is tapered with respect to a plane perpendicular to an axial direction of the reel hub 111 in such a manner that a radially outer side of the lower face is inclined upward in the drawing. An upper face of the lower flange 113 is tapered in such a manner that a radially outer side of the upper face is inclined downward in the drawing.
Recently, in order to record enormous amounts of information data in a small space, according to digitalization and downsizing of magnetic recording apparatuses, an intention is to improve recording density. The magnetic tape has been made thinner for improvement of volumetric recording density, and tracks have been made narrower for improvement of planar recording density.
Recently, in order to record enormous amounts of information data in a small space, according to digitalization and downsizing of magnetic recording apparatuses, it is intended to improve recording density. The magnetic tape has been made thinner for improvement of volumetric recording density, and tracks have been made narrower for improvement of planar recording density.
However, because the magnetic tape has been made thinner, the magnetic tape has become likely to be deformed in a lateral direction. For example, there have been some cases in which the magnetic tape has deformed in a lateral direction during fast feeding or at acceleration or deceleration of the tape in a recording and reproducing apparatus, and has locally got in touch with a guide roller and so on intensively, resulting in occurrence of a curve or a weaving of the magnetic tape. In addition, there has been a tendency that due to the deformation of the magnetic tape, the lateral ends of the magnetic tape may get in touch with the lower face of the upper flange or the upper face of the lower flange to generate abrasion powder, and dropouts may be increased.
Meanwhile, as the tracks of the magnetic tape have been made narrower, a so-called linearity defect is likely to happen such that reproducing output in the deformed area of the tape may become lower than reproducing output in a rectilinear area. Therefore, even a minute deformation of the tape may result in the linearity defect. As a result, the aforesaid weaving of the magnetic tape will incur and increase the linearity defect, in other words, there will be a variation of the reproducing output.
Moreover, because the magnetic tape has become narrower, so-called irregular winding may occur in some cases, when the magnetic tape has been wound around the reel hub. Also, and as shown in FIG. 6, which is an enlarged perspective view of a part A of FIG. 5, a part of the end of the magnetic tape may jump out from a plane formed by the ends of the magnetic tape 120. As shown in FIG. 6, the part 120a of the end of the magnetic tape that jumps out will be deformed weavingly like sea weed. In the case where the magnetic tape has deformed like sea weed, normal recording and reproduction cannot be expected. Therefore, it is extremely important to prevent such irregular winding.
Although various factors have been considered as causes of the irregular winding, it is considered that one cause is air that may enter between adjacent magnetic tapes when the magnetic tape 120 is wound around the reel hub 111 of the tape reel 110, and the magnetic tape may be pushed upward while the air escapes. In the case of a conventional magnetic tape having a thickness of about 10 xcexcm for example, the irregular winding has been able to be restrained by providing a groove in the reel hub 11 of the tape reel. It is considered that because the tape had a large thickness and relatively high rigidity, the magnetic tape could have been wound without involving air by such a measure.
However, as the magnetic tape has become thinner and thinner, it has become more and more difficult to restrain the irregular winding, even though the groove has been provided in the reel hub. It has been found that the irregular winding is likely to happen especially in a case where the thickness of the tape is 7 xcexcm or less.
Meanwhile, it has been found that almost all of the abrasion powder occurring when the ends of the magnetic tape get in touch with the lower face of the upper flange and the upper face of the lower flange is powder generated through abrasion of a back layer. As shown in FIG. 6, the magnetic tape 120 has been heretofore in a shape of parallelogram in cross section. A magnetic recording medium having a large width will inevitably take such a shape when it has been cut by means of a rotary cutter to form the magnetic tape 120. Accordingly, a large amount of the abrasion powder is generated from a part B where an end of the back layer has projected from ends of a magnetic layer and a nonmagnetic layer in a lateral direction of the magnetic tape.
The present invention has been made in view of the above described problems, and its object is to provide a magnetic tape cassette, a tape reel and a magnetic tape in which output variation or dropout can be restrained, and which can perform more accurate recording and reproduction. Particularly, an object of a first embodiment of the invention is to provide the tape reel around which the magnetic tape can be smoothly wound, in which occurrence of deformation in a lateral direction of the magnetic tape and irregular winding can be restrained, and which can perform more accurate recording and reproduction. Further, an object of a second embodiment of the invention is to provide the magnetic tape in which an amount of abrasion powder occurring when the ends of the magnetic tape get in touch with the lower face of the upper flange and the upper face of the lower flange is decreased, and which can perform more accurate recording and reproduction.
The inventors of this invention have had an intensive study and found that deformation of the magnetic tape in a lateral direction and irregular winding can be remarkably restrained by decreasing a distance between the upper flange and the lower flange in the tape reel into a determined distance. Conventionally, it has been considered that if the distance between the upper flange and the lower flange has been decreased, the magnetic tape would be unable to be smoothly wound around the tape reel. However, by setting this distance between the upper flange and the lower flange to be the determined distance taking a width of the magnetic tape into consideration, the magnetic tape can be smoothly wound around the tape reel, and the deformation of the magnetic tape in a lateral direction and occurrence of the irregular winding can be restrained.
Specifically, the first aspect of the present invention is a tape reel comprising an upper flange and a lower flange respectively provided at an upper end and a lower end of a cylindrical reel hub around which a magnetic tape is wound, characterized in that a maximum value of a distance from the upper flange and the lower flange to lateral ends of the magnetic tape is 0.5 mm or more, and less than 1.0 mm.
Moreover, in a case where a thickness of the magnetic tape is 6 xcexcm or more, and less than 11 xcexcm, the deformation of the magnetic tape in a lateral direction and occurrence of the irregular winding can be more reliably restrained.
On this occasion, in a case where the lower face of the upper flange and the upper face of the lower flange are respectively tapered, a distance from the ends of the outermost magnetic tape which has been wound around the tape reel to the lower face of the upper flange and the upper face of the lower flange will become xe2x80x9ca maximum value of the distance from the upper flange and the lower flange to the lateral ends of the aforesaid magnetic tapexe2x80x9d. In a case where the lower face of the upper flange and the upper face of the lower flange are in parallel to each other, the distance from the upper flange and the lower flange to the lateral ends of the aforesaid magnetic tape is constant.
Further, the inventors have found as a result of their intensive study that the occurrence of abrasion powder can be remarkably decreased by a construction where an end of the back layer does not project from an end of a nonmagnetic layer in a lateral direction of the magnetic tape.
Specifically, the second aspect of the present invention is a magnetic tape comprising a nonmagnetic substrate, a magnetic layer provided on one face of the nonmagnetic substrate and a back layer provided on the other face of the nonmagnetic substrate, the magnetic tape being adapted to be wound around a tape reel having an upper flange and a lower flange respectively provided at an upper end and a lower end of a cylindrical reel hub, characterized in that in a state where the magnetic tape is wound around the tape reel, a distance from the upper flange and the lower flange to lateral ends of the back layer is larger than a distance from the upper flange and the lower flange to lateral ends of the nonmagnetic substrate or lateral ends of the magnetic layer.
Further, the distance from the upper flange and the lower flange to the lateral ends of the back layer may be larger than both the distance from the upper flange and the lower flange to the lateral ends of the nonmagnetic substrate and to the lateral ends of the magnetic layer.